<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div span {
            font-weight: 200;
            font-size: 13px;
        }
        .ww{
            background-color: darkturquoise;
        }
    </style>
</head>
<body class="ww">
<div >
<h1>不好玩</h1>
<span>单独的div内容</span>
<div class="nav">
    <h1>这是一段文本内容，其中<span>不要看，字太小了</span></h1>
</div>
</div>
</body>
</html>